1. Field of the Invention
The present invention relates to a method for treating alumina and, more particularly, to a method of providing an alumina having increase slurry life.
2. Description of the Background
Alumina in slurry form is used in a wide variety of applications. Alumina slurries are used in frictionizing paper surfaces, fiberglass surfaces and metal surfaces, as anti-static and soil protection on wool, nylon and acrylic carpets, as a dispersion agent in rug shampoos, as anti-static and anti-soil agents, as binders for vacuum cast alumina silica fibers, as a sintering aid, and for coating ceramic monoliths for auto exhaust catalysts. The aluminas commonly used in such applications are the aluminum oxyhydroxide, particularly the alpha alumina monohydrates. To form such alumina slurries, the alumina is placed into a dispersion or suspension using a peptizing agent such as an acid as, for example, hydrochloric acid, nitric acid, etc. Alumina slurries, unless stabilized in some manner, tend to viscosify rapidly, forming thick gelatinous materials (gels), thereby making them difficult to use in the commercial applications described above. Accordingly, it becomes important to maintain a prepared alumina slurry at a desired, low viscosity for as long as possible.
It is known from U.S. Pat. No. 4,191,737 that alumina slurries can be stabilized by treatment with hot water and bubbling carbon dioxide through the alumina slurry. Similarly, British Pat. No. 904,411 teaches the stabilization of alumina slurries by bubbling a carbon dioxide medium therethrough.
It is also known, as taught by Feldkamp, et al, J. Pharmaceutical Sci. 70, pp. 638-640 (1981) and Scholtz et al, J. Pharmaceutical Sci. 74 (4), p. 478 (1985) that carbonate formed on the surface of alumina will alter the rheology and gellation rate of alumina/water dispersions.